Objectives: In hypertension, the vascular wall undergoes morphological changes that alter mechanical responses to vasoactive substances. Ceramide is a recently identified second messenger synthesized in response to cytokines such as tumour necrosis factor α (TNF-α). It has been previously demonstrated that vascular smooth muscle cells (VSMC) from genetically hypertensive rats proliferate at a higher rate than those of normotensive origin. We tested the hypothesis that the ceramide pathway is impaired in VSMC from spontaneously hypertensive rats (SHR). Design: VSMC were isolated from aortae of SHR and from Wistar-Kyoto (WKY) rats. Ceramide levels were measured under baseline and agonist-stimulated conditions and cell proliferation was monitored. Methods: Cell proliferation was determined by cell counting. Ceramide levels were determined via radioactive labelling, high-performance thin-layer chromatography and phosphorimaging. Relative mRNA levels of neutral sphingomyelinase were determined using semiquantitative polymerase chain reaction (PCR). Results: Basal ceramide levels in untreated cells were lower in cells from SHR compared to WKY rats. During chronic treatment with TNF-α, ceramide levels increased in WKY rat cells but remained unchanged in cells from SHR. TNF-α treatment had an inhibitory effect on WKY rat VSMC proliferation, but stimulated proliferation in cells from SHR. Short-term incubation with TNF-α resulted in a greater increase in ceramide in cells from WKY rats than those from SHR. Semiquantitative PCR analysis indicated that neutral sphingomyelinase mRNA may be reduced in SHR VSMC. Conclusions: We conclude that ceramide synthesis is impaired in vascular smooth muscle from SHR and may contribute to increased VSMC proliferation in hypertension.
- Cultured vascular smooth muscle
- Spontaneously hypertensive rats
ASJC Scopus subject areas
- Internal Medicine
- Cardiology and Cardiovascular Medicine